Field of the Invention
The present invention relates to an image reading device, an image forming system, and a program.
Description of the Related Art
Conventionally, among image forming systems including a printer that can perform duplex printing and an image reading device that includes scanners, there is one that measures and adjusts front and back positions of images formed on a sheet, using one scanner (for example, see JP 2006-072075 A).
The conventional technology described in JP 2006-072075 A reads the front and back positions of the images formed on the sheet with one scanner, and thus conveys the sheet twice. Therefore, a time required for conveyance to read the images on the sheet is increased as the operation to read the front and back positions of the images is performed for each sheet. As a result, productivity as the image forming system is decreased.
Therefore, to avoid conveyance of the sheet twice for each sheet, there is one that reads the front and back positions of the images formed on the sheet, using two scanners. To be specific, one of the two scanners reads the image formed on a surface of the sheet, and the other of the two scanners reads the image formed on a back surface of the sheet. Accordingly, the images respectively formed on the front and back of the sheet can be read by conveying the sheet only once per sheet.
However, there is a mechanical difference in the scanners. That is, there is a machine difference. Therefore, even if the images formed on the front and back of the sheet are read using two scanners having the same performance, misregistration may be caused between the read positions of the two scanners. Therefore, the front and back positions of the images formed on the sheet may not be accurately read.
Further, in a case of mechanically adjusting the machine difference between the scanners, high component accuracy and high position accuracy are required. Therefore, the cost to adjust the machine difference between the scanners is increased.
By the way, front and back misregistration sometimes occurs in the images formed on both surfaces of the sheet even though setting on the printer side is not changed, as the duplex printing advances by the printer. Such front and back misregistration of the images occurs due to environmental conditions such as humidity in a print location and deterioration of mechanical durability. Therefore, the front and back misregistration of the images caused by the environmental conditions may be suddenly caused.